The first-pick central defender, who has a reputation for playing through injury, suffered a back problem in training last week and missed Saturday's 2-0 win at Fulham that took Chelsea to the top of the Premier League.

Mourinho would not, however, rule Terry out completely.

"Today he is worse than yesterday, tomorrow maybe he is the same or better," Mourinho said after Saturday's game.

Mourinho is likely to stick with experienced Champions League campaigner Andriy Shevchenko though the 30 million pound ($57 million) striker has yet to shine for his new club.

Germany captain Michael Ballack, suspended for three domestic games after being sent off last week, will also return in midfield.

Mourinho has indicated he will field his strongest available side despite Levski's status as the also-rans of Group A.

"We need the points," he said. Chelsea, who beat Werder Bremen 2-0 at home in their group opener, still have to face Barcelona at home and away.

Mourinho would not, however, rule Terry out completely.

"Today he is worse than yesterday, tomorrow maybe he is the same or better," Mourinho said after Saturday's game.

Levski's Brazilian-born left back Lucio Vagner will return to their starting line-up after missing the defeat at Barcelona due to suspension.

With Valeri Domovchiyski struggling with injury and his strike partner Emil Angelov doubtful, Stoilov may turn to the Bulgarian premier league's top scorer Georgi Ivanov, who is yet to start in Europe this season.

Ivanov's double inspired Levski to a 3-0 win at lowly Rodopa Smolyan on Friday that took them to the top of the league.

A wave of euphoria has swept through Sofia before Chelsea's visit with match tickets sold out in less than five hours last Wednesday.